Regular drivers on the A9 will be witnessing the painfully slow progress of dualling the road between Perth and Inverness.

In the latest section of roadworks, vehicles have been slowed to 40mph for several miles south of Aviemore since last summer.

By the look of things this week, it is still some way away from being finished, which is due to be this summer.

But that stretch is just the first few of 80 miles of dual carriageway which are still due to be completed by 2025.

That is in just eight years’ time - and yet it’s nearly a decade since the SNP pledged to dual the road after coming to power in 2007.

Ministers have described the scale of the “mammoth” project as the largest in Scottish history, and it will indeed be a gargantuan task to complete so much in so little time.

We also still don’t know exactly how much it’s going to cost.

For at least the last six years, there has just been the unchanging estimate of £3 billion, which alone is more than twice as much as the Queensferry Crossing - itself the biggest scheme in a generation.

I’m told things won’t get any clearer until construction contracts for the 12 sections of dual carriageway have been awarded.

However, that may not be for another two years, on the basis of the scant information about the project’s timescales that is currently available.

Things are equally vague over where such huge sums will come from.

All we know is that a range of financing options are still being considered and no final decision has been taken.

It is true that much preparatory work has been done, with design contracts together worth up to £180m alone awarded - but even that work isn’t complete.

That itself throws up the very real possibility that the planning process, which includes the compulsory purchase of several homes to make way for the widened road, will see objections that trigger more public inquiries.

The next section to be dualled is scheduled to get underway by the end of the year, between Luncarty and Birnham, which will extend the dual carriageway north of Perth.

Yet that is one of several stretches where preliminary work had been started more than ten years ago by the previous Labour-Liberal Democrat administration.

After the SNP took over, it was to be an “early priority” - yet that was nine years ago.

I’m told that the Scottish Government’s Transport Scotland agency, which is in charge of the scheme, remains on target to complete half the dualling - that’s 40 miles - by 2022, i.e. in five years’ time.

By comparison, it took around eight years to build less than 50 miles of the A74(M) to the Border in the 1990s.

Completion of the A9 project is also officially on schedule, although officials do acknowledge the programme is ambitious.

I could be completely wrong about this, but the timescales just don’t seem realistic. To achieve them, the A9 would have to become one giant set of roadworks.

Back in 2008, three years before ministers announced the 2025 completion date, Transport Scotland told me that dualling the A9 was a “long-term investment plan - taken forward in stages, as funding and resources are available”.

The project may yet revert to that previous status.

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